Mol Pain
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Preclinical studies on pathological pain rely on the von Frey test to examine changes in mechanical thresholds and the acetone spray test to determine alterations in cold sensitivity in rodents. These tests are typically conducted on rodent hindpaws, where animals with pathological pain show reliable nocifensive responses to von Frey filaments and acetone drops applied to the hindpaws. Pathological pain in orofacial regions is also an important clinical problem and has been investigated with rodents. ⋯ In the acetone spray test, the duration of orofacial responses was significantly prolonged in oxaliplatin-treated mice. The response frequencies to laser light stimulation were significantly increased in Nav1.8-ChR2 mice treated with oxaliplatin. Our sheltering tube method allows us to reliably perform the von Frey, acetone spray, and optogenetic tests in orofacial regions to investigate orofacial pain.
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Cadaverine is an endogenous metabolite produced by the gut microbiome with various activity in physiological and pathological conditions. However, whether cadaverine regulates pain or itch remains unclear. In this study, we first found that cadaverine may bind to histamine 4 receptor (H4R) with higher docking energy score using molecular docking simulations, suggesting cadaverine may act as an endogenous ligand for H4R. ⋯ Calcium imaging analysis showed that cadaverine perfusion enhanced calcium influx in the dissociated dorsal root ganglion (DRG) neurons, which was suppressed by JNJ-7777120 and capsazepine, as well as in the DRG neurons from Trpv1-/- mice. Patch-clamp recordings found that cadaverine perfusion significantly increased the excitability of small diameter DRG neurons, and JNJ-7777120 abolished this effect, indicating involvement of H4R. Together, these results provide evidences that cadaverine is a novel endogenous pruritogens, which activates H4R/TRPV1 signaling pathways in the primary sensory neurons.
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The anterior cingulate cortex (ACC) is critical for pain perception, emotion and cognition. Previous studies showed that the ACC has a complex network architecture, which can receive some projection fibers from many brain regions, including the thalamus, the cerebral cortex and other brain regions. However, there was still a lack of whole-brain mapping of the ACC in adult mice. ⋯ We also found that cortical neurons in the ACC mainly receive ipsilateral monosynaptic projections. Some cortical areas and forebrain regions also bilaterally projected to the ACC. These findings provide a complete analysis of the afferents to the ACC in adult mice, and whole-brain mapping of ACC afferents would provide important anatomic evidence for the study of pain, memory, and cognition.
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Methylene blue (MB) has been shown to reduce mortality and morbidity in vasoplegic patients after cardiac surgery. Though MB is considered to be safe, extravasation of MB leading to cutaneous toxicity has been reported. In this study, we sought to characterize MB-induced cutaneous toxicity and investigate the underlying mechanisms. ⋯ Thus, using a novel rat model of MB-induced cutaneous toxicity, we show that infiltration of 1% MB into cutaneous tissue causes a dose-dependent pro-inflammatory response, highlighting potential roles of IL-6, IL-1β, and Fos. Thus, anesthesiologists should administer dilute MB intravenously through peripheral venous catheters. Higher concentrations of MB (1%) should be administered through a central venous catheter to minimize the risk of cutaneous toxicity.
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Background: Recent studies have demonstrated that activated microglia were involved in the pathogenesis of central sensitization characterized by cutaneous allodynia in migraine. Activation of microglia is accompanied by increased expression of its receptors and release of inflammatory mediators. Acupuncture and its developed electroacupuncture (EA) have been recommended as an alternative therapy for migraine and are widely used for relieving migraine-associated pain. ⋯ Results: Allodynia increased of c-Fos, and activated microglia were observed after repeated IS stimulation. EA alleviated the decrease in mechanical withdrawal thresholds, reduced the activation of c-Fos and microglia labeled with Ibal-1, downregulated the level of microglial purinoceptor P2X4, and limited the inflammatory response (NLRP3/Caspase-1/IL-1β signaling pathway) in the TNC of migraine rat model. Conclusions: Our results indicate that the anti-hyperalgesia effects of EA ameliorate central sensitization in IS-induced migraine by regulating microglial activation related to P2X4R and NLRP3/IL-1β inflammatory pathway.